User guide

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101
DMX512
Input
The DMX512 input connects directly to the output of a standard
RS485
or RS422 receiver such as the 75176. The base address of the
received
block of twelve channels is set via the keypad and stored in eeprom.
The DMX512 data is merged with the analogue inputs on a highest
takes
precedence basis.
The Good Rx indicator is an open collector output, suitable for
connection
to a 20 mA LED. The output sinks current when DMX512 errors are
detected.
Analogue
Input
The Analogue inputs are routed through the AL2001 as shown in the
application drawings. The DMX512 data is merged with the analogue
inputs on a highest takes precedence basis. The circuitry must be
calibrated such that the maximum voltage is 5V at the AN_xxx
inputs.
Zero Cross
The AL2001 requires a zero cross for each phase. The circuit will
operate on single phase in which case all zero cross inputs must be
commoned. The Zero Cross input provides synchronisation to the
mains
frequency. An active low pulse at the mains zero cross point (i.e.
twice the mains frequency) is required. The pulse width should be in
the order of 100uS. It is imperative that this input be a 'clean', fast
rise time pulse. Any jitter at the Zero Cross input will produce
flickering on the outputs.
The external 4539 multiplexor is used to ensure that the REDZC
input
is always connected to a source of zero cross pulses. Should the red
zero cross fail, the AL2001 will select one of the other phases to
ensure continued operation.
Temperature
Sensor
The temperature sensor is calibrated over a range of 5V. The
following
bands are defined:
• 0V - 1.37V High temperature fault, causes output switch off and
fan drive
• 1.56 - 2.15V High temperature warning, causes fan drive
• 2.2V - 5V Within normal tolerance.
The temperature input is disabled by connection to AVCC. The above
voltages assume that AVCC=5V.